The integrity of fluid transmission systems in aircraft is critical to the safety of the aircraft and a great amount of effort has been expended in the development of such systems which are substantially failsafe. Because of the spatial limitations present in aircraft and the need for carrying fluids to all areas of the plane, the fluid systems therein necessarily comprise an intricate web of tubing, valves and couplings. One of the weak aspects of these systems is the couplings for connecting sections of tubing and a variety of components to the overall tubing system. The most critical problems with respect to these couplings result from the limited space available in which to install these assemblies.
Well known couplings can be adapted for use in these high pressure systems, however, they generally suffer a serious drawback in that they require axial alignment of the tubing before a secure connection can be achieved. Axial alignment is extremely difficult to accomplish under the installation conditions present in aircraft and invariably will result in a union which is prestressed, inhibiting an effective seal as well as inducing undesirable stresses in the transmission line itself. As the aircraft vibrates during normal operation, the tubing is subjected to further stressing. The additive effect of these two stresses may reach or exceed the allowable maximum which may either cause immediate failure or significantly shorten the useful life due to its prematurely fatiguing.
It is therefore a primary object of the coupling of this invention to eliminate the need for accurate axial alignment of the tubular members to be connected and to provide a coupling which is pre-stressed in a manner which enhances the effective seal of the connection.
More specifically, it is an object of this invention to provide a lightweight, high pressure, high temperature coupling having a very thin flange in stressed mating relation with a spherical seat element.
Attempts to overcome the above mentioned problems are represented by the coupling devices described in U.S. Pat. Nos. 3,067,187 to Collins and 3,273,917 to Chakroff. These devices utilize spherical sealing surfaces which, however, result only in a single line sealing contact and a very limited ability to accommodate misalignment.